This invention relates to a GPS receiving apparatus that receives signals from a GPS (Global Positioning System) satellite and measure the position and speed of the signal receiving apparatus. In particular, the present invention relates to a GPS apparatus that is capable of being held by or attached to a human arm to measure the position of a human who is walking or running, as well as moving speed and moving distance.
The GPS system has 24 GPS satellites revolving at a rate of 12 hours per one turn on six orbits at an inclination angle of 55 degrees above approximately 20,200 Km around the earth. The navigation data required for position location is transmitted from at least three to four or more satellites and received by a receiver installed on the earth so that a mobile body having the receiver mounted thereon may have its position location calculated, including the relative position, the moving speed, etc. It is also possible to determine a velocity vector of the mobile body by measuring a Doppler frequency contained in a carrier wave. Although in FIG. 3 the transmission wave by the GPS involves two kinds, i.e., L1 with a frequency of 1.57542 GHz and L2 with a frequency of 1.22760 GHz, the ordinary position location utilizes L1. L1 is subjected to PSK modulation by a pseudo noise code (a synthetic wave of a C/A code for satellite identification and navigation data such as satellite orbit information, time information, etc.) and spread spectrum, for transmission. The 1.57542-GHz signal received by an antenna 300 is amplified by an L-passband amplifying circuit 301, converted by a down-converter means 302 into a first IF (intermediate frequency) signal of several tens of MHz to 200 MHz, and further rendered into a second IF signal of approximately 2 MHz to 5 MHz. The second IF signal is inputted to a voltage comparator 303 so that it is digital-converted by a clock of several times the IF signal by using the voltage comparator 303. The output of the comparator 303 is spread spectrum data. In a message decoding circuit 304, the digital data outputted by the voltage comparator 303 is subjected to spread spectrum by a C/A code that is the same pseudo noise code as that of the satellite, thereby obtaining carrier wave phase information corresponding in pseudo distance to navigation data. This operation is performed with respect to a plurality of satellites so that a position location calculating means 306 may accurately determine position data from the navigation data. Typically, such data is acquired from four satellites. The position data determined by the position location calculating means 306 is outputted to a CPU that performs controls on all operations of portable apparatuses or devices. Or otherwise, it is outputted outside as a digital signal. As the size reduction in GPS receivers advances, considerations have been made for utilizing the GPS receivers for purposes of determining human running motion and walking distance as disclosed in Unexamined Published Japanese Patent Application No. H6-118156.
However, many problems are present where the conventional GPS receiver is to be utilized for measuring the moving speed or moving distance of human bodies. In the interest of portability, it is desired that such a receiver be compact and capable of being carried on the arm. However, when considering the case of attaching it to the human arm, there is a disadvantage in that the moving speed of a person when walking or running per se cannot be measured due to variations in the position to be identified resulting from back-and-forth arm swing relative to the direction of advancement of the human body or the difference between the moving speed of the human body and the arm swing speed. FIG. 4 shows a typical diagram of speed information to be obtained when the GPS receiving apparatus is carried on the arm of a person running. In FIG. 4, the abscissa denotes elapsed time and the ordinate denotes speed, while a broken line represents the mean body moving speed and a solid line denotes arm swing speed. The duration that the arm swing speed is increasing with respect to the mean body moving speed corresponds to the period of time that the arm is being forwardly swung. In this instance, the arm swing speed is higher than the body moving speed. Conversely, when the arm is swung in a direction of the human body opposite to the advancing direction, the arm speed is lower than the mean body moving speed. The intersections a, b with the mean moving speed are the points that the arm speed and the mean body moving speed become equal to each other. In this manner, the GPS receiving apparatus when carried on the arm is affected by the movement. In order to measure the body mean moving speed in this state, there is a necessity of operating the GPS receiving apparatus by applying a frequency twice or higher the frequency of arm swinging to conduct speed measurement and then integrate the results thereof. However, this method is nothing more than the continuous operation of a high-power-consumption GPS receiving apparatus, and involves significant hindrance to the realization a portable and small-sized apparatus such as that having a watch type configuration. There also has been a problem in that, besides the speed, when the GPS receiving apparatus is carried on the arm in order to obtain location information during walking or running, accurate measurement is impossible due to the effect of the arm swing motion.